C# 密封类（开发人员如何使用）

public sealed class Animal
{
    public string Species { get; set; }

    public void MakeSound()
    {
        Console.WriteLine("Generic animal sound");
    }
}

// The following code will cause a compilation error because 'Animal' is sealed and cannot be inherited:
// public class Dog : Animal // Error: Cannot inherit from sealed class 'Animal'
// {
// }

Public NotInheritable Class Animal
	Public Property Species() As String

	Public Sub MakeSound()
		Console.WriteLine("Generic animal sound")
	End Sub
End Class

' The following code will cause a compilation error because 'Animal' is sealed and cannot be inherited:
' public class Dog : Animal // Error: Cannot inherit from sealed class 'Animal'
' {
' }

public class Animal
{
    public string Species { get; set; }

    // A virtual method allows derived classes to override it.
    public virtual void MakeSound()
    {
        Console.WriteLine("Generic animal sound");
    }
}

public class Dog : Animal
{
    // The sealed override prevents further overriding of this method.
    public sealed override void MakeSound()
    {
        Console.WriteLine("Bark!");
    }
}

Public Class Animal
	Public Property Species() As String

	' A virtual method allows derived classes to override it.
	Public Overridable Sub MakeSound()
		Console.WriteLine("Generic animal sound")
	End Sub
End Class

Public Class Dog
	Inherits Animal

	' The sealed override prevents further overriding of this method.
	Public NotOverridable Overrides Sub MakeSound()
		Console.WriteLine("Bark!")
	End Sub
End Class

public sealed class ControlledClass
{
    // A sealed property that prevents overriding.
    public sealed string ControlledProperty { get; set; }

    // A method that cannot be redefined by derived classes.
    public virtual sealed void ControlledMethod()
    {
        // Method implementation
        Console.WriteLine("Executing controlled method.");
    }

    // A sealed event that cannot be subscribed to or raised by derived classes.
    public sealed event EventHandler ControlledEvent;

    // Sealed indexers, if applicable
    public sealed string this[int index]
    {
        get { return "Value"; }
        set 
        { 
            // Setter implementation 
        }
    }
}

Public NotInheritable Class ControlledClass
	' A sealed property that prevents overriding.
	Public NotOverridable Property ControlledProperty() As String

	' A method that cannot be redefined by derived classes.
	Public Overridable NotOverridable Sub ControlledMethod()
		' Method implementation
		Console.WriteLine("Executing controlled method.")
	End Sub

	' A sealed event that cannot be subscribed to or raised by derived classes.
	Public Event ControlledEvent As EventHandler

	' Sealed indexers, if applicable
	Default Public NotOverridable Property Item(ByVal index As Integer) As String
		Get
			Return "Value"
		End Get
		Set(ByVal value As String)
			' Setter implementation 
		End Set
	End Property
End Class